According
to most, it is derived from the word praya (tapas) and chitta (resolve or firm belief).
Thus it signifies tapas performed with the firm belief that it will redeem past sins.

The system of religious atonement for an offence was prevalent among the Aryans even
before they came to India. In India, the Samvidhana Brahmana of
the Sama Veda (see Veda) is the earliest work to detail a
system of penances. Law books like the Manusmriti also describe the various modes of
atonement prevalent in ancient India. Prayashchit forms one of the three important parts
of the sacred law of the Hindus. The other two are vyavahara (procedure) and achara
(religious custom).

In earlier times, religious and judicial punishments were differentiated.
Civil offenders, after serving their allotted term of punishment, had also to observe a
religious penance before being accepted back in society. Sins are classified into five
categories: mahapataka (mortal sins), atipataka (highest sins), pataka (great sins),
prasangika (due to contact with sinners), upapataka (minor sins).

The five mahapatakas are Brahmahatya - murder of a Brahmin, Surpan - drinking liquor,
Svarna-sneya - theft of gold, Guru talpa gamana - sexual intercourse with the wife of
one's guru, and Shishu hatya - destruction of an unborn child. Perpetrators of the above
became social outcastes or patita.

Then there are sins that are committed unknowingly and those that are committed
knowingly. For those committed unknowingly, it is universally agreed that their effects
are destroyed by the recitation of Vedic mantras and the performance of penances. However,
opinions are sharply divided on sins committed knowingly. According to Manu and Gautama,
the effects of all sins are destroyed by the performance of prayashchit. According to
Yajnavalkya however, prayashchit does not destroy these sins but morally re-arms the
repentant, who thus become fit to associate with others again. However, the results of
these sins still have to be borne. The expiation of sins is extremely important because of
the dread of suffering in one's future birth (seeMoksha).
This resulted in some very severe penances. Many diseases and natural infirmities were
viewed as the consequence of sins from a previous existence. Lepers for instance, were
required to do penance in order to expiate crimes of former births. When a sinner was
deemed a social outcaste, he was not permitted to attend any social function or ceremony.
Anyone who interacted with him was considered an equal sinner. The sinner's re-inclusion
into society was allowed only after the prescribed prayashchit was performed.

For this reason, even today loads of pilgrims go to holy places called tirthas to expiate their sins and Brahmins are fed and
generously awarded during all ceremonies. When a person is about to die, listening to
Vedic mantras is said to rid him of all his sins. The relatives of a dead person immerse
his ashes in a holy river so that all his sins are washed away and he goes straight to
heaven. The Ganga, Yamuna and Narmada are especially sacred for these last rites.

Fasting of any kind is a very popular form of prayashchit. Sometimes the sinners
inflict pain on them by walking on burning coals, sleeping on sharp-edged glass or pointed
nails.

Since the cow is believed to be sacred, everything connected with it is said to be
purifying. The five products of the cow or Panchagavya are to be swallowed during various
penances.

Reading and reciting Vedic mantras is another form of penance. Religious gifts to
Brahmins or the poor are also recommended giving away gold, silver, grain or food equal to
one's weight is a common practice even today.

Prayashchit practice even today. Going on pilgrimage (see Tirtha)
is another form of expiation. In present times, it is usually these milder forms of
penance that are observed. Severe punishments like ordeals by fire are now illegal.